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POPHP invalid image's and error handling
 

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  1. POPHP invalid image's and error handling
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    <p>Using PHP's Image and GD functions you can use the following method to finally output the php image</p> <pre><code>imagepng($image); </code></pre> <p>Sometimes, for whatever reason the image may not be displayed typically the error is not with the image but with the actual php functions not executing successfully. However this causes a blank image to be returned which doesn't help me.</p> <p>What I want to know is, is there a way to detect a blank or an invalid image and create a new image, write the errors to the new image using imagestring() and then display this new (debug) image instead.</p> <p>for example, a successfully displayed image with no errors:</p> <pre><code>$image = imagecreate(256, 256); //create image imagecolortransparent($image, $BLUE); //set transparent imagefilledrectangle($image, 0, 0, 256, 256, $BLUE); //fill with 'transparent colour' //Draw a border round the image imageline($image, 0, 0, 0, 255, $Black); imageline($image, 0, 0, 255, 0, $Black); imageline($image, 255, 0, 255, 255, $Black); imageline($image, 0, 255, 255, 255, $Black); imagestring($image, 1, 10, 10, "I am an image!", $Black); imagepng($image); imagedestroy($image); </code></pre> <p>but if I then introduce some errors in the php script that may or may not be to do with the actual image creation then the php script fails and the image will not be visible...</p> <pre><code>$image = imagecreate(256, 256); //create image imagecolortransparent($image, $BLUE); //set transparent imagefilledrectangle($image, 0, 0, 256, 256, $BLUE); //fill with 'transparent colour' //Draw a border round the image imageline($image, 0, 0, 0, 255, $Black); imageline($image, 0, 0, 255, 0, $Black); imageline($image, 255, 0, 255, 255, $Black); imageline($image, 0, 255, 255, 255, $Black); imagestring($image, 1, 10, 10, "I am an image!", $Black); /* I am here to cause problems with the php script ** and cause the execution to fail, I am a function ** that does't exist... ** ** and I am missing a semi colon! ;)*/ non_existant_function() imagepng($image); imagedestroy($image); </code></pre> <p>At this point I want to create a new image like above but in replacement of the I am an image! text I would put the actual error that has occured.</p>
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    1. USMatt Slaney
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    1. COWith the specific example you've taken, you'd have a Parse error *(syntax error : no semi-colon)*, which means the PHP script would not even start its execution ;; and if you add the semi-colon, you'll have a Fatal Error *(calling a non-existing function)* ;; in either case, there is nothing you can do : you cannot recover from those -- best solution is to watch the log files of your server.
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      1. USPascal MARTIN
    2. COp.s. If the image is not detected before trying to be displayed in the browser the error below is provided. The image "genimage.php?Number=4" cannot be displayed, because it contains errors. I am actually downloading the said php image and using it within an application and so it would be helpful for me to write the errors as a new image and send that instead. Also, the error actually provided in the browser is pretty useless to me because I kno it contains errors... I want to know the usual PHP stuff... The line number of the problem, the assumed issue, etc... Thanks.
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      1. USMatt Slaney
    3. COOne final thing Is there a way also to simply not return the image and instead write a more comprehensive error message... one that actually provides a bit more insight as to where in my php script the error occured
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      1. USMatt Slaney
 

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